1. Field of the Invention
This invention relates to the field of vehicle-carrying trailers, and in particular to a drawbar trailer for safely carrying rapid transit subway cars, large railroad cars and other very long, very heavy loads over roads.
2. Description of the Prior Art
Trailers for carrying vehicles are well known, however, such trailers most frequently are substantially larger than the vehicle carried, and often are adapted to carry a plurality of such smaller vehicles. Where relatively large vehicles must be carried, for example large construction equipment, tracked vehicles and the like, flat-bed trailers are normally employed. Even in such cases, the usual trailer is much larger than the vehicle carried.
In order to carry a vehicle which is large in comparison to vehicles most frequently encountered on roads, some provision must be made to assist in steering. Roads are engineered such that only vehicles of certain maximum distance between the front and rear wheels can be accommodated in the space allowed for curves, hills and the like. If a trailer is composed of a series of articulated, connected subelements, a large collection of such elements can follow the path taken by the lead element, and thereby be accommodated upon roads dimensioned for maximum-length vehicles of the size of one sub-element. However, where the load is to be a large rigid body, even independently-steerable sub-elements will not alter the large length of the carried body.
A device adapted for transporting railway cars on streets is disclosed in U.S. Pat. No. 2,058,955--Culemeyer. This device seeks to attach the wheels of the railroad car to individual four wheel bogies, each bogy supporting a short length of rail. In order to mount a railway car on the Culemeyer bogies, the bogies for the front and rear are connected to one another by rail elements in addition to the rail carrier by each bogy, or the unconnected bogies are positioned immediately behind one another, whereby each axle of the railway car may be rolled onto its supporting rail links one at a time. Having been loaded, the railway wheels rest in depressions which tend to position the bogies immediately under the railway wheels. It will be appreciated that the device of Culemeyer is effectively a wheel adaptor which allows steel wheeled railway cars to traverse roads by merely attaching road tires to the axles of the railway car, under the steel wheels. Culemeyer therefore employs the frame and body of the railway car for the necessary rigidity in the vehicle as carried over the roads. Inasmuch as the bogies comprise spring suspensions in addition to the track-rated spring suspensions normally carried by railroad cars, the overall device may be expected to be somewhat unstable and prone to sway if carried at a great speed or over uneven terrain. It will be difficult for a designer using the Culemeyer device to arrive at a resilience in the suspension of the bogies which will provide a stable overall structure when supporting a railway car having its own suspension of unknown attributes.
Culemeyer employs a drawbar-driven steering mechanism for the individual bogies. Rigid linkages attach the drawbar to the bogies on each side of the front axle support, a rotational element of variable length transmitting the steering forces to the rear bogies. The steering mechanism employed is invariable in that whenever the drawbar moves to one side, the front bogies are steered to follow the drawbar and the rear bogies are steered in the opposite direction, whereby the carried vehicle will follow a path having a somewhat tighter turning radius than would otherwise result. The individual bogies are not individually controllable, but rather follow this one steering scheme. It is therefore impossible to cause the trailer to steer under any control other than the drawbar, and impossible to cause the trailer to follow a diagonal path or a complex path.
Various trailers known in the art employ multiple wheel members, wheel members connected to follow complex steering patterns, and vertically-positionable wheel suspensions. In U.S. Pat. No. 3,520,549--DeLay, a semitrailer is equipped with a plurality of steerable axles. Although not driven by a drawbar, the front axles follow the pulling vehicle, and the rear-most axles steer in the direction opposite the front axles. Additional axles located in the mid-section do not steer but remain longitudinally aligned.
U.S. Pat. No. 3,131,950--Weaver, Jr. et al discloses a device for leveling a load passing over uneven terrain. Manually-driven threadable positioning mechanisms are provided for each end of each axle, whereby the user can adjust both the vertical distance between the load-carrying platform and the axles, and the relative angle between the axle and the platform. It will be appreciated that, in order to employ such individually-adjustable means with a drawbar trailer having multiple front and multiple rear axles, some means must be included for adjusting each axle to the same angle and height. If this is not done, the axle which happens to be positioned at the lowest level with respect to the rigid platform will suffer the greatest wear and will in effect carry the other axles.
A variety of devices are known for carrying very large loads. Examples of devices for carrying large loads disclosed in the art include large steel beams (U.S. Pat. No. 4,017,094) and tanks (U.S. Pat. No. 3,191,962). In carrying such large loads, there are various problems in addition to merely increasing the scale of the usual vehicle. Using a larger vehicle does not change the fact that the roads are dimensioned to accommodate smaller vehicles, and of course, the truck or trailer designer cannot avoid the large dimensions of the load.
When the large load to be carried is a vehicle, the problems are compounded. Means must be provided for loading the vehicle onto the trailer. As cranes sufficiently large for such a purpose are quite expensive, it is desirable to roll the vehicle onto the trailer. Once loaded, some provision must be made to secure the vehicle from movement with respect to the trailer. Inasmuch as the carried vehicle has its own suspension, either the resilience of the vehicle's suspension must be accommodated, or some means must be provided to cancel or otherwise secure the vehicle against rocking and swaying.
The present invention is directed to carrying rapid transit subway vehicles, railway cars and the like over streets. This form of transportation may at first seem peculiar, as every city with a rapid transit system is part of a rail network anyway, and the gauge of track is usually the same.
However, the realtively "fine" suspensions of such rapid transit vehicles would be destroyed by even a brief journey on typical railroad freight track. Moreover, the couplers of such cars are usually not compatible with typical railroad stock. Use of railroad flatcars is possible, but less practical, as cranes would still be necessary and bridge and tunnel clearances would present difficulties. Passenger cars intended for modern rapid transit systems simply can therefore not be safely or conveniently transported over typical heavy duty, general purpose railroad tracks. This invention therefore allows such rapid transit vehicles to be transported from a manufacturing facility, even one without a rail siding, or from one passenger railroad system, to another passenger railroad system, over the roads.
The invention, however, departs from the prior art by employing a plurality of front and rear axles which are not only steerable according to a regime intended to reduce the turning radius of the trailer, but in addition, by employing axles which are independently controllable by manual controls disposed at convenient locations around the trailer. Accordingly, the trailer can be effectively parallel parked by diagonal movements, adapted to follow a predetermined steering radius by independently steering only the front or only the rear axles, or locked in stable non-steering position to efficiently traverse straight road sections. In this way, the trailer can be aligned with a section of track with relative ease.
The invention comprises movable means for raising and lowering any portion of the trailer platform with respect to any other portion, the means being a fluid-driven inter-related means which permits an entire side of the trailer to be subject to the same control, or the entire front or entire rear thereof. With such means, the trailer may be tilted to an inclined plane for receiving the railway vehicle, which is merely pushed and/or drawn onto the trailer. In order to traverse banked turns which are designed for smaller vehicles, traveling at higher speed, the trailer platform is transversely positionable at selected heights, whereby the platform may be held level, or in an orientation which is substantially closer to level, while the axles are sloped. Each of these functions is controllable either manually or automatically.
The suspension of the carried vehicle is effective only during loading and unloading. Although the wheels of the carried vehicle remain in contact with the platform, the body of the carried vehicle is engaged by movable support means which may be pivoted into position under the body of the carried vehicle. Most often, rapid transit vehicles are themselves provided with vertically-positionable bodies, whereby the vehicle may be raised on its suspension, the supporting members may be positioned and the carried vehicle lowered thereupon. This procedure securely locks the body of the carried vehicle to the trailer, and eliminates any destabilizing effect which might otherwise result from the effect of the suspension of the carried vehicle.
The invention is also useful in carrying other kinds of very long, very heavy loads, such as liquid and gas storage tanks, construction beams and others.